Hydroprocessing of hydrocarbon feedstocks is often used to convert lower value hydrocarbon fractions into higher value products, such as conversion of vacuum gas oil (VGO) feedstocks to diesel fuel and lubricants. Typical hydrocracking reaction schemes can include an initial hydrotreatment step, a hydrocracking step, and a post hydrotreatment step. After these steps, the effluent can be fractionated to separate out a desired diesel fuel and/or lubricant oil basestock. However, the requirements for production of diesel boiling range fuels can potentially vary during the course of a year. During summer months, a primary goal of hydroprocessing can be reduction of sulfur and/or nitrogen content of diesel boiling range fuels in order to satisfy regulatory requirements. Sulfur reduction can also be important during winter months, but an additional consideration can be improving the cold flow properties of the diesel boiling range fuels. Dewaxing is required when highly paraffinic oils are to be used in products which need to remain mobile at low temperatures, e.g., lubricating oils, heating oils and jet fuels. The straight chain normal and slightly branched paraffinic substituents which are present in oils of this kind are waxes which cause high pour points and high cloud points in the oils. In heavy oils, cyclic paraffins and aromatics having paraffinic side chains are also present as wax. If adequately low pour points are to be obtained, these waxes must be wholly or partly removed, or converted to non-waxy analogues. Thus, catalyst dewaxing of diesel boiling range fractions can be used to provide improved cold flow properties.
However, during the refinery cycle, hydrotreatment (HDT) activity and dewaxing activity of the dewaxing catalysts decreases as coke accumulates on the catalyst. Typically, the spent catalysts are disposed of or sent to a third party for metals reclamation. During the reclamation process, the catalyst support, e.g., a zeolite, is destroyed, and the catalyst metals are recovered. Consequently, fresh catalyst must be produced from materials, such as zeolites, base metals and/or noble metals. Thus, there is a need for regeneration and rejuvenation methods for restoring HDT and dewaxing activity to spent catalysts, so that catalysts may be reused without the need for constantly producing fresh catalyst.
U.S. Pat. No. 8,394,255 describes methods for integrated hydrocracking and dewaxing of a feed under sour conditions for formation of diesel and lubricant boiling range fractions.
U.S. Provisional Patent Application No. 62/270,213 describes base metal dewaxing catalysts, methods for making the base metal dewaxing catalysts, and methods for performing dewaxing using such catalysts.
U.S. Provisional Patent Application No. 62/270,234 describes methods for dewaxing distillate boiling range feeds, such as distillate boiling range feeds suitable for fuels production.